Improved ordering : using ttMove and pvMove

README.md

@@ -26,13 +26,14 @@ C++ chess engine
 
 | Rank | Name          | Elo   | +/- | Games | Score | Draw  |
 | ---- | ------------- | ----- | --- | ----- | ----- | ----- |
-| 1    | radiance_3.0  |   242 |  25 |   960 | 80.1% | 10.6% |
-| 2    | radiance_2.4  |   226 |  24 |   960 | 78.6% | 12.7% |
-| 3    | radiance_2.3  |   169 |  22 |   960 | 72.6% | 14.8% |
-| 4    | radiance_2.2  |    -5 |  20 |   960 | 49.2% | 18.0% |
-| 5    | radiance_2.1  |    -8 |  20 |   960 | 48.9% | 17.8% |
-| 6    | radiance_2.0  |   -44 |  20 |   960 | 43.7% | 16.6% |
-| 7    | radiance_1.5  |  -178 |  23 |   960 | 26.5% | 10.4% |
-| 8    | radiance_1.4  | -1002 | nan |   960 |  0.3% |  0.0% |
+| 1    | radiance_3.1  |   334 |  23 |  1600 | 87.2% |  8.6% |
+| 2    | radiance_3.0  |   196 |  18 |  1600 | 75.5% | 10.1% |
+| 3    | radiance_2.4  |   195 |  18 |  1600 | 75.4% | 12.3% |
+| 4    | radiance_2.3  |   143 |  17 |  1600 | 69.5% | 11.8% |
+| 5    | radiance_2.2  |   -23 |  16 |  1600 | 46.7% | 12.2% |
+| 6    | radiance_2.1  |   -51 |  16 |  1600 | 42.8% | 10.8% |
+| 7    | radiance_2.0  |   -70 |  16 |  1600 | 40.1% | 10.1% |
+| 8    | radiance_1.5  |  -343 |  26 |  1600 | 12.2% |  0.0% |
+| 9    | radiance_1.4  |  -881 | 126 |  1600 |  0.6% |  0.0% |
 
 _I'm radiant!_

include/SearchMaterialistNegamax.h

@@ -114,7 +114,7 @@ class SearchMaterialistNegamax : virtual public Search
 		else
 		{
 			Search::generateMoveList(b, moveList, /*legalOnly=*/ true, /*onlyCapture=*/ false);
-			Search::orderMoves(b, moveList);
+			Search::orderMoves(b, moveList, (rootMoves[0].pv.size() > ss->ply) ? rootMoves[0].pv[ss->ply] : cMove());
 		}
 
 		for (const cMove &move : moveList)
@@ -126,6 +126,7 @@ class SearchMaterialistNegamax : virtual public Search
 
 			ss->currentMove = move;
 
+			Key key = b.m_s->materialKey;
 			// 16. Make the move
 			b.movePiece(move, s);
 
@@ -139,11 +140,11 @@ class SearchMaterialistNegamax : virtual public Search
 			else
 			{
 #ifdef transposition
-				auto it = transpositionTable.find(b.m_s->materialKey);
+				auto it = transpositionTable.find(key);
 				const bool found = it != transpositionTable.end();
-				if (found && it->second.second > depth - 1)
+				if (found && std::get<1>(it->second) > depth - 1)
 				{
-					score = it->second.first;
+					score = std::get<0>(it->second);
 					if (score > VALUE_MATE_IN_MAX_DEPTH)
 						score -= ss->ply;
 					else if (score < VALUE_MATED_IN_MAX_DEPTH)
@@ -187,9 +188,9 @@ class SearchMaterialistNegamax : virtual public Search
 					if (score != VALUE_DRAW)
 					{
 						if (!found)
-							transpositionTable[b.m_s->materialKey] = std::pair<Value, UInt>(score, depth - 1);
-						else if (it->second.second <= depth - 1)
-							it->second = std::pair<Value, UInt>(score, depth - 1);
+							transpositionTable[key] = std::tuple<Value, UInt, cMove>(score, depth - 1, move);
+						else if (std::get<1>(it->second) <= depth - 1)
+							it->second = std::tuple<Value, UInt, cMove>(score, depth - 1, move);
 					}
 #endif
 				}
@@ -242,7 +243,15 @@ class SearchMaterialistNegamax : virtual public Search
 
 					// Fail high
 					if (score >= beta)
+					{
+						auto it = transpositionTable.find(key);
+						const bool found = it != transpositionTable.end();
+						if (!found)
+							transpositionTable[key] = std::tuple<Value, UInt, cMove>(score, depth - 1, move);
+						else if (std::get<1>(it->second) <= depth - 1)
+							it->second = std::tuple<Value, UInt, cMove>(score, depth - 1, move);
 						break;
+					}
 					else
 						alpha = score;  // Update alpha! Always alpha < beta
 				}

include/search.h

@@ -27,7 +27,7 @@ inline TimePoint now()
 }
 
 namespace {
-	std::unordered_map<Key, std::pair<Value, UInt>> transpositionTable;
+	std::unordered_map<Key, std::tuple<Value, UInt, cMove>> transpositionTable;
 	TimePoint remaining = 0;
 }
 
@@ -334,20 +334,47 @@ class Search
 
 	struct MoveComparator
 	{
-		MoveComparator(BoardParser &b) : b(b) {};
+		MoveComparator(const BoardParser &b, const cMove &move1, const cMove &move2) : b(b), move1(move1), move2(move2) {};
 
 		bool operator() (const cMove &m1, const cMove &m2) const
 		{
+			if (move1 != cMove())
+			{
+				if (move1 == m1)
+					return true;
+				else if (move1 == m2)
+					return false;
+			}
+			if (move2 != cMove())
+			{
+				if (move2 == m1)
+					return true;
+				else if (move2 == m2)
+					return false;
+			}
 			return (m1.isCapture() && m1.getFlags() != 0x5 ? Int((*b.boardParsed())[m1.getTo()]->value()) - Int((*b.boardParsed())[m1.getFrom()]->value()) : 0) >
 				(m2.isCapture() && m2.getFlags() != 0x5 ? Int((*b.boardParsed())[m2.getTo()]->value()) - Int((*b.boardParsed())[m2.getFrom()]->value()) : 0);
 		}
 
-		BoardParser &b;
+		const BoardParser &b;
+		const cMove &move1;
+		const cMove &move2;
 	};
 
-	static void orderMoves(BoardParser &b, std::vector<cMove> &moveList)
+	static void orderMoves(const BoardParser &b, std::vector<cMove> &moveList, cMove pvMove = cMove())
 	{
-		std::sort(moveList.begin(), moveList.end(), MoveComparator(b));
+		// Search pvMove is in movelist. Speed up comparision if not.
+		if (pvMove != cMove() && std::find(moveList.begin(), moveList.end(), pvMove) == moveList.end())
+			pvMove = cMove();
+
+		auto it = transpositionTable.find(b.m_s->materialKey);
+		const bool found = it != transpositionTable.end();
+		cMove ttMove = found ? std::get<2>(it->second) : cMove();
+		// Search ttMove is in movelist. Speed up comparision if not.
+		if (ttMove != cMove() && std::find(moveList.begin(), moveList.end(), ttMove) == moveList.end())
+			ttMove = cMove();
+
+		std::sort(moveList.begin(), moveList.end(), MoveComparator(b, pvMove, ttMove));
 	}
 
 	/**